Various types of blood sampling apparatus are known in the art. The following patent documents are believed to represent the state of the art: U.S. Pat. Nos. 3,877,465; 4,763,648; 4,920,970; 4,934,015; 4,981,140; 5,002,066 & 5,084,034; European Patent Application 88906129.7 and PCT Published Patent Application WO 93/21821.